1 : depends on your DAW, some of them have a built-in bridge (making the possibility to use a 32bit plugin in a 64bit DAW), some not and then you'd have to use a 3rd party software, though I can't certify any of this since i'm using Reaper who bridges a very stable way. A big drawback at least in reaper is that bridged plugins have sometimes a laggy UI, and also the bridge application make their window "out" of reaper, if ever you see what I mean. In the case of reaper, bridging works 100% perfectly, it's just the UI sometimes has some delay (for example in this case it's harder to see VU meters in some plugins). I don't know if this happens with other bridging apps.
2 : in my use as an enlighted hobbyist, I see no other advantage. Certain specific uses could benefit from it more, but I don't know them. Imo, it's only worth it if you really really need more than those 3 or 3.25 Gb of RAM. I'm gonna switch back to using reaper 32 bit because I don't need this even if in a big project because I print most of things anyway, and also cause reaper allows running any plugin as a dedicated process (with its own 3Gb allocated RAM) transparently, which will suffice for my own needs, without the tiny annoyance of plugin bridging.